File operation for copying content of one file to another

#  Copying content of 1.txt file to 2.txt after creation of file
#  Please provide the 1.txt file in the current folder as input and
#  check after runing the program in the same folder for 2.txt

I=open('1.txt',"r")
O=open('2.txt',"w")
for l in I.readlines():
    O.write(l)
I.close()
O.close()

Exceptional handling for Zero Division Error

# if value of x is given as zero the zero divison error generates and program terminates
x=int(raw_input('Enter the number of students failed:'))
y=100/x
print y


# If x is not defined itself the program not terminated instead it goes to except loop
try:
    x=int(raw_input('Enter the number of students failed:'))
    y=100/x
    print y
except ZeroDivisionError:
    x=1
    y=100/x
    print y